Muffler



DCC- 21, 1943- Q. G. NOBLITT ETAL 2,337,300

' MUFFLER Filed Sept. 2, 1941 al; 3.: El

MMMIMHIUIIIIIIIIMHUIIM Patented Dec. 21, 1943 MUFFLER Quintin G. Noblitt and Edmund Ludlow, Columbus, Ind., assignors to Nobiitt-Sparks Industrics, Inc., Columbus, 1nd., a corporation of Indiana Application September 2, 1941, Serial No. @9,239

2 Claims.

both tuned and untuned. In addition, we divide l0 the gases into two or more components, cause the components to now over paths of different lengths, and then recombine them to silence sounds of more or less delinite wave lengths as the result of interference effects. the gases are subjected to the action of the untuned side silencing chambers before being divided.

The accompanying drawing illustrates our in- Desirably,

vention, Fig. 1 being a longitudinal section 20 through a silencer and Fig. 2 a transver e section on the line 2 2 of Fig. l.

The muffler illustrated in the drawing cornprises a cylindrical shell IE which, indicated in Fig. 2, is conveniently of a general elliptical shape in cross-section, but which may have any convenient cross-sectional form. The front and rear ends of the shell I0 are close-d respectively by heads II and I2. Spaced longitudinally from these heads and from each other are two transverse partitions I3 and I4 through which there extend three tubes I5, l', and I1. The front end of one of these tubes, here shown as the tube I5, is connected to an inlet nipple i3 which extends through the iront head II and is adapted at its front end for connection to the exhaust pipe of an internal combustion engine. Another of the tubes, shown as the tube I5, communicates at its rear end with an exhaust nipple i@ which projects rearwardly through the head i2 40 and is adapted at its rear end for connection to a suitable tail pipe.

Between the front head II and the partition i3 we mount a transverse partition 2l which co-operates with the head I I to define a silencing chamber 22 and with a partition I3 to define a transverse passage 23 interconnecting the front ends of the tubes i5 and I1. A similar partition 24 near the rear end of the casing Ii) co-operates with the head I2 to define a second silencing 50 chamber 25 and with the partition I to denne a transverse passage 26 interconnecting the rear ends of the tubes I5 and I'I.

Extending through the partition 2| is a tube 30 providing a restricted neck through which 55 the silencing chamber 22 communicates with the passage 23. A similar tube 3| extending through the partition 2&3 provides communication between the silencing chamber 25 and the passage 2t. As is well known each of the chambers 22 and 25, with its associated neck 3S or Si, serves to absorb sounds of more or less deiinite frequency depending upon the volume of the chamber and upon the cross-sectional area and length oi the neck.

As will 'be clear from Fig. l, the tube E5 is provided with a multiplicity of periorations extending throughout its length, such perforations desirably being in the for-in of narrow, circumferentially extending slots 33. The space between the partitions I. is preferably divided into a plurality of silencing chambers 34, and 3l by transversely extending partitions 3S.

As so far described, the mufller of this application is the saine as that set forth in our copending application, Serial No. @$233, of even ling date herewith. Tha mulder of this application, however, difiers from that of the other in that the conduit formed by the alined tube I6 and discharge nipple i8 is not provided with an opening permitting the direct admission of gases from the transverse passage 26. Instead, the tube iii and discharge nipple I5 have a reasonably tight telescoping t which prevents any gases from entering from the transverse passage 25. An additional difference between the muilier of this application and the inuilier of our other application just mentioned lies in the fact that for a limited portion of its length the tube i5, and desirably also the tube il, is provided with a multiplicity oi perorations 33 similar to those in the tube i5. As shown, both the tube i5 and the tube i7 are provided with such perforations; and in the case of each tube the portera-tions are confined to that portion of the tube lying within the rearniost side silencing chamber 37.

In the operation of the muiiler above described, the exhaust gases enter the front end of the tube I5 through the nipple I8. As they pass through the tube i5, some of the gases in highpressure Zones pass outwardly through the openings 33 into the side chambers 34, 3S, 35, and 37 and return to the tube when low-pressure zones pass therethrough. Thus, the chambers 3Q, 35, S6, and 3l act as untuned, or as relatively broadly tuned, side silencing chambers tending to suppress sounds over a fairly wide range of frequencies.

Some of the gases escaping from the tube I5 through the openings t3 into the silencing chamber 37 will flow transversely of the muller and enter the tube l@ through the openings $3 therein. To a certain extent, the saine sort of transverse gas-ilovv can exist through the chamber Si from the tube il to the tube it. However, the larger portion ci the gases entering the tube lli will flow therethrough and enter the transverse passage from which they Will escape through the tube il, transverse passage and tube l@ to the exhaust nipple it. Because oi the difference etween the lengths oi the paths followed by the gases entering the tube i@ from the compartment t? and the gases which flour through the tube ll and transverse passage interference efects will occur 'when the gases are recombined in the tube ifi; as is Well known, such interference eiects Will tend to silence sounds of more or less definite frequency.

As pointed out in more detail in our copend ing application above referred. to, the arrangement of slots and chambers sli to il? adapted to suppress relatively high sound reduencies over a fairly broad band, the silencing chambers and are respectively adapted to suppress incre or less definite hl relatively low frequencies, While the interference phenomena occurring Within the tube are adapted to suppress a more or less deiinite frequency lying Within an intermediate range. As in the device oi such fio-pending application th'3 possibility oi gas-flow through the chamber i in the tube l5 rectly into the tube l permits a portion oi the gases, aiter having been subjected to the silencaction ci the chambers and lli and the slots associated with t1 n, to enter the rear portion of the tube l Without passing through the tube lll and iront portion ci the tube l@ and Without subjected to the action of the silencing chambers and Similarly, the slots in the rear portion oi the tube il' permit a second portion oi the citer having been subjected to tbe silencing a the tube l5 of tb tubeV ld Without passing thro tions of the tubes l and il e subjected to the action ci the ber The division of the gases into portions which follow paths of diierent lengt1v s before being re*- conlbined and discharged from the silencer not only causes the in rter-ence phenomena which are effective to suppress sounds of intermediate frequency but also reduces bach pressure, as moi front por- 'tbout being it ly explained in our co-pending application, Serial No. @$9,238. ln the silencer of this appliation, l cir-fever, there are a plurality of paths of different lengths over which the gases may flow;

as a result, the interierence phenomena created when the gases recornbue tend to suppress sounds of a nuinber of frequencies rather than sounds of a more or less denite single frequency, as in the silencer of our other application.

W e claim as our invention:

l. In a silencer, an elongated caf iront and rear ends, a of partitions isposed in said ce .ng and from the ends ci the casing and from eap passage interconnecting tie first tube the rear end of tubes, means providing a t the fr second and third tubes, a tuned ber communicating with one ci passages, a supplementary ti tion subdividlng the space between se titicns and within the casing, said n both sides oi said suppl said th d tube only in rear of sa. partition being proviu c with a mult longitudinally distributed openings Dro tricted communication between the interior he respective tubes the space surrouneing 2. In a silencer, an elongated having front and rear ends, a pair ci transverse partitions disposed in said and spaced from the ends of the casing and from other, three tubes extending longitudinally oi the cassaid tubes, means providing a rear transverse passage interconnecting the rear end or" tube and the rear end of the second of said tuba` means providing a front transverse terconnecting the front ends of the third tubes, a tuned silencing chanib nicating with one of said transve and a supplementary transverse :lai vidlng the space between said and Within the casing, said rst t sides oi said supplementaiy partition vided with a multiplicity of longitudinally dise tributed openngs providing restricted ooinrnuni` cation between the interior of such tube the space surrounding it, and said third tube be ig provided in rear oi said partition v th an o ing providing restricted communication with ne space surrounding it whereby a portion of the gases admitted to said niet tube can dow transversely of the casing from said irst tube to said third tube through the space in rear or" supplementary partition, said second and third tubes in advance of said partition having imperiorate Walls.

EDMUND LUDLOVJ. QUNTN (fr. NCBLITT. 

